The present invention relates to a photofinishing system wherein images of a wide variety of types such as photographic images from an inkjet printer are laminated in a subsequent operation. More particularly the present invention relates to such a system having a buffer between the inkjet printer and the laminator for transporting the printed images from the inkjet printer to a laminator.
In photofinishing operations it is conventional to develop and print photographs on roll stock photographic paper having a width that generally accommodates one size of print. After printing out a roll of photos on a strip of the roll stock, the strip is cut to provide the individual prints. Dedicating a given size of roll stock to the production of a given size photo is less flexible for fulfilling print orders and slows throughput. It requires the photofinishing operation either to have multiple machines, each dedicated to a given size of photo or it places a burden on the operator to change the print media from one size to another after completing orders.
Advancements in photofinishing allow for the production of photographs by ink jet printers, laser printers and other photofinishing printers including silver-halide systems that receive digital input and employ conventional wet chemistry output. Moreover the use of computers in connection with these advancements allows for further improvement. For example, it is not necessary to use roll stock having the width of a desired finished photo. A photofinishing printer now can generate photos of various sizes on a single sheet of print media. Also the images can be manipulated to nest various image sizes on a single larger sheet. Accordingly, a sheet or roll stock of a single width can be used to generate prints of various sizes for a single customer order.
Currently, the photofinishing printer of choice is an inkjet printer. Inkjet printing comprises a scan and print technology involving an intermittent indexing of the print medium. In this respect the print medium such as photographic paper is fed to the printer and is held stationary by the printer while an inkjet print head makes a printing scan across the paper. The paper then is indexed for a second scan of the print head. In this fashion a plurality of scans will generate the photographic image.
Inkjet prints historically have been subject to problems such as durability and fading because of limitations put on ink systems used in inkjet printers. For example the printed image can be eroded by abrasion. Both the durability and fading problems are solved by the application of a protective laminate to the image after printing. A protective laminate is applied by passing the print continuously through a laminator in order to apply a protective transparent layer to the surface of the print. While lamination provides an acceptable solution to image problems associated with inkjet prints, the start and stop indexing motion inherent in inkjet printing conflicts with the operation of a laminator, which typically operates with continuous motion.
Accordingly, to applicant""s knowledge and for the reasons noted above, an inkjet printing system and a laminator system have not been linked in a continuous sequential operation and heretofore a sheet comprising the print output of an inkjet printer was not directly fed into a laminator. Instead the printed sheets were simply removed from the printer and accumulated for later feeding one at a time to a laminating device.
Feeding the printed sheet output of an inkjet printer to a laminator presents several problems. For example, the inkjet printer used in photofinishing operations typically can produce printed sheets in a variety of lengths. Thus a transport mechanism for feeding the printer output to the laminator must be able to accommodate each of the various lengths of prints that are output by the printer. Also, in order to minimize space, it is preferred that the transport mechanism receive a leading portion of the printed sheet from the printer while a trailing portion is still in the grip of the printer. Thus a leading edge of the printed sheet should enter the transport mechanism before the sheet is completely printed. However, when the leading edge of the partially printed sheet is in the grip of the transport mechanism, the transport mechanism must not interfere with the start/stop indexing motion of the portion of the sheet still in the printer. Any resistance to this motion or any attempt of the transport mechanism to tug on the sheet prior to the completion of the printing operation will likely degrade the print quality.
After the printing operation is completed, the printer will eject the printed sheet at a continuous speed that generally is faster than the start/stop indexing motion of the printing operation. The transport mechanism must accommodate this faster movement of the sheet and then deliver the sheet to the laminator. As the transport mechanism moves the leading edge of the sheet to the laminator, the laminator will grip the leading edge and tend to draw the sheet from the transport mechanism. To prevent damage to the sheet or the printed image, the transport mechanism must offer no resistance to the drawing out of the sheet.
Thus a transport mechanism for disposition between an inkjet printer and a laminator must have several attributes. It should be able to accommodate various sizes of prints up to the longest produced by the printer. It must not interfere with printing by resisting the start/stop indexing motion of the inkjet printing operation or attempt to tug on a partly printed sheet. It also should allow rapid deployment of the sheet from the printer at the end of the printing operation, convey the sheet to the laminator and not resist the drawing of the sheet from the buffer by the laminator.
Accordingly, it is an object of the present invention to provide a transport mechanism for handing off a work piece from one device to another wherein the devices have different processing speeds.
Another object of the present invention is to provide a transport mechanism between an ink jet printer and a laminating device for delivering a printed sheet from the printer to the laminator wherein the laminator has a faster processing speed than the printer.
A further object of the present invention is to provide a transport mechanism for receiving a printed sheet output of an inkjet printer and delivering the printed output directly to a laminator wherein the transport mechanism accommodates two processing speeds of the printer and a single operating speed of the laminator.
Yet another object of the invention is to provide a method for delivering a printed sheet produced at a first processing speed by an inkjet printer to a laminator operating at a different processing speed.
In the present invention, a transport mechanism is provided that includes a buffer disposed to receive a printed page output of an inkjet printer and deliver the printed page or sheet to a coater/laminator that applies a protective lamination to the printed surface. The sheet moves through the printer at a first speed during the printing operation, the first speed being the average of a start/stop movement required for inkjet printing namely a peak speed during the indexing of the paper and a stoppage or pause for printing. The printed output then ejects from the printer at a speed that is faster than the first (average) speed. Subsequently, the printed sheet moves through the laminator at yet another speed usually faster than the average first speed.
The buffer, disposed between the printer and laminator, includes a track that defines a path of travel long enough to accommodate the longest sheet produced by the printer. The buffer receives the printer output in a manner that accommodates the two speeds of the printer without interfering with the operation of the printer. The buffer then delivers the printer output to the laminator in a manner that accommodates the operating speed of the laminator.
The buffer includes driven rollers arranged along the track for moving the printed sheet through the buffer preferably at a constant speed that is between the eject speed of the printer and the operating speed of the laminator. Each of the rollers includes a one way clutch that allows the rollers to overrun a drive shaft in response either to the ejection of a printed sheet from the printer or to the laminator tugging on a sheet leaving the buffer. In addition, the driven rollers include a slip clutch between a drive motor and the drive shaft that limits the drive force exerted by the rollers on a printed sheet. This prevents the driven rollers from tugging so hard on a sheet that is still within the grip of the inkjet printer at a time prior to ejection that the image quality is reduced.
Accordingly, the present invention may be characterized in one aspect thereof by a transport buffer for transporting a flexible sheet along a path of travel between an outlet of a first workstation and an inlet of a second workstation, the first workstation intermittently delivering the flexible sheet to the buffer at a first peak speed and a first average speed in a first mode of operation (such as an inkjet printing operation) and continuously delivering the flexible sheet to the buffer at a second speed in a second mode of operation(such as when the printed sheet is ejected from the printer), and the second workstation taking up the flexible sheet at a third speed, the buffer comprising:
a) a drive roller arranged along the path of travel for engaging and moving the flexible sheet through the buffer, the drive roller being operatively connected to a motor for driving the rollers at a substantially constant drive speed;
b) a first clutch having a predetermined torque limit allowing slippage of the drive roller when the constant drive speed is greater than the speed at which the flexible sheet is moving from the first workstation and into the buffer; and
c) a second clutch allowing the drive roller to rotate at a speed faster than the constant drive speed to permit movement of the flexible sheet into the buffer from the first workstation at a speed greater than the constant drive speed.
In another aspect, the present invention may be characterized by a method of transporting a flexible sheet moving from a first workstation operating at a first average speed and a first peak speed faster than the average speed in a first mode of operation and at a second speed in a second mode of operation, to a second work station operating at a third speed greater than the first average speed comprising;
a) engaging the sheet leaving the first workstation with a rotating driver for moving the sheet along a path of travel at a constant speed from the first workstation to the second workstation;
b) limiting the torque applied by the rotating driver for moving the sheet in the buffer when the constant speed is greater than the speed at which the sheet is moving from the first work station; and
c) freeing the rotating driver to rotate at a speed greater than the constant speed to permit movement of the sheet into the buffer at a speed greater than the constant speed.